Abstract: An apparatus for supplying a respiratory gas to a patient includes a respiratory gas generating device, a device for introducing the respiratory gas into the cavitas nasi of the patient, a conduit fluidly connected to the respiratory gas generating device and the introducing device; a valve, provided in the conduit, for separating and connecting the introducing device from and to the respiratory gas generating device and an orifice provided in the conduit upstream of the valve means. The apparatus for supplying the respiratory further includes a controller for operating the valve between intermittent and continuous mode. In the intermittent mode, the valve connects the introducing device to the respiratory gas generating device at a predetermined interval to provide the respiratory gas in the form of a pulse, and in the continuous mode, the valve continuously connects the introducing device to the respiratory gas generating device.